Intraoperative medial pivot kinematics in cruciate-retaining total knee arthroplasty are associated with a higher Forgotten Joint Score.

Abstract

Achieving medial pivot (MP) kinematics during flexion after total knee arthroplasty (TKA) is considered important for restoring physiological knee function. However, few studies have explored the association between intraoperative MP patterns and patient-reported outcomes such as the Forgotten Joint Score-12 (FJS-12), which is less prone to ceiling effects. This retrospective study included 46 patients who underwent primary cruciate-retaining (CR) TKA using a multi-radius femoral component. Intraoperative kinematic analysis with an imageless navigation system was used to classify patients into an MP group (n = 24) and a non-MP group (n = 22), based on whether the lateral femoral condyle showed greater posterior translation than the medial condyle during flexion. Clinical outcomes were evaluated 1 year postoperatively, including the FJS-12, the Hospital for Special Surgery Knee Score (HSS), and the new Knee Society Score (KSS), with subscale analysis. The MP group had significantly higher FJS-12 scores than the non-MP group (73.3 vs. 50.1; P < 0.001). While no significant difference was found in HSS scores, the MP group showed significantly better KSS subscale scores for symptoms, satisfaction, expectation, and functional activity. An intraoperative MP pattern was significantly associated with superior patient-reported outcomes at 1 year after TKA, particularly higher FJS-12 and KSS scores. These findings suggest that achieving MP kinematics during surgery may contribute to improved functional recovery and greater patient satisfaction.